That passage, of course, ties into what the Defense Professor says in the latest chapter: "You cannot use the Killing Curse, so the correct tactic is to Apparate away." If I had to work from the premise that the revision is actually related to that, I'd assume it's emphasising the Defense Professor being, in fact, a Dark wizard.

But I agree that from a point of view outside Eliezer's head, it appears to have at best neutral impact, and at worst negative impact on the effect of the passage.